1. Field of the Invention
The invention relates to anti-foaming agents and to the use thereof in detergent compositions.
2. Description of the Related Art
Handwashing involves introducing water into a bucket or soaking vessel, and machine-assisted handwashing involves introducing water into the washing drum of a washing machine. Subsequently, the desired amount of detergent is dispensed. By manual stirring or running the washing machine, foam is produced. In the next step, the dirty laundry is immersed and left to soak for 10 to 30 min. In the case of handwashing, after this period, the laundry is washed manually to remove soiling. In the case of washing machines, the wash cycle is started (duration: about 60 minutes). Significant foaming during the wash cycle is interpreted as good cleaning action of the detergent.
In the course of rinsing, the excess wash liquor is poured away and the textiles are wrung out to remove the excess wash liquor absorbed. The rinse cycles consist of addition of fresh water, rinsing of the textiles to remove detergent residues, pouring the rinse liquor away and wringing of the textiles to remove the rinse liquor absorbed. In general, these rinse cycles are repeated until no further foam is visible (4 to 5 times). The formation of foam during the rinse cycle is associated with the presence of detergent, which is undesired.
In order to reduce water consumption and protect the environment, it would therefore be desirable to have an anti-foaming agent which barely affects foaming in the wash cycle, if at all, and gives lasting suppression of new foam in the rinse cycle. This could reduce the number of rinse cycles and hence the amount of water consumed.
U.S. Pat. No. 4,637,890 describes a granular detergent composition which results in reduced foaming and reduced turbidity of rinse water during the rinse cycle which follows a wash cycle, the composition comprising a surfactant, a water-soluble detergency builder, foam control prills comprising a silicone oil as a foam suppressant, and additionally fatty acid soaps and a quaternary ammonium salt.
The anti-foaming agent in this case only becomes active at low pH; in the wash cycle at pH values of >9 it is inactive. In the case of handwashing or machine-assisted handwashing, and in the case of machine washing, these high pH values are typically not attained in non-industrial use, and so the defoaming action sets in prematurely in the wash cycle.
U.S. Pat. No. 4,894,117 describes a composition of an agglomerated granular material for the delayed release of an anti-foaming agent in a wash liquor. These antifoam granules exhibit delayed release by virtue of the silicone anti-foaming agent being encapsulated by cellulose.
EP 254 499 B1 discloses a silicone defoaming composition which is obtained by reaction of a mixture of a trimethylsilyl-terminated polydimethylsiloxane and a silanol-terminated polydimethylsiloxane with a polyoxyethylene-polyoxypropylene copolymer and with silica. Use as an anti-foaming agent in detergent compositions is not described.
The technology utilized in the two documents mentioned above is the encapsulation of silicones or silicone defoamers, these substance classes having strong anti-foaming action. The activity of the retarded anti-foaming action in the rinse cycle depends on the release of these active ingredients, which in turn depends on many parameters, for example the temperature of the liquor and the duration of the individual steps. Therefore, the use of these systems is possible exclusively in the case of machine washing, where reproducible conditions exist with regard to temperature and duration. In the case of handwashing or in the case of machine-assisted handwashing, these systems cannot be used because of different washing practices. On the other hand, a product having retarded anti-foaming action or foam suppression irrespective of external parameters in the rinse cycle in the case of handwashing or in the case of machine-assisted handwashing is also effective in the case of machine washing.
WO 2011/107361 A1 and WO 2011/107397 A1 describe, as an anti-foaming agent, a polyether-containing aminosiloxane or a powder comprising a polyether-containing aminosiloxane on a carrier substance, and also the production process for and the use of this anti-foaming agent in detergent compositions for handwashing and machine washing, the anti-foaming agent not displaying its anti-foaming action until during the rinse cycle. The aminosiloxane which forms the basis of the anti-foaming agent contains a terminal polyether fragment. The active ingredients used are thus polyether-containing aminosiloxanes which do not display delayed anti-foaming action or foam suppression until the rinse cycle, and which are difficult to prepare. Such materials are produced in practice by equilibration reactions proceeding from OH-terminated polydimethylsiloxanes, α,ω-polyether-functional siloxanes and hydrolysates of the corresponding aminoalkylsilanes. A disadvantage is that the synthesis thereof often results in biphasic reaction mixtures, since the polyethersiloxane is incompatible with the rest of the components because of different polarities.
EP 685 250 A1 discloses the use of a mixture of an aminosiloxane and a finely divided silica in detergents for prevention of foaming during the rinse cycle.
A disadvantage of these mixtures is that the defoaming action sets in prematurely in the wash cycle and is not delayed until the rinse cycle. In the case of handwashing or in the case of machine-assisted handwashing, significant foaming is desirable in the wash cycle and is interpreted as a sign of good cleaning action of the detergent and hence of cleanliness.